1. Field of the Invention
The present invention relates to a printing data processor for use with a printer.
2. Related Art
Generally, a printer receives from a host, such as a personal computer, printing data written in a page description language (hereafter referred to as PDL). A PDL includes drawing data, patterns and an expansion rule. By combining those three components, various kinds of pages are described.
More specifically, by combining descriptions of all components, data on the state or mode of printing is reproduced, such as color or monochrome, whether a binary or multi binary (or multi-value) monochrome image is printed, and whether on one side or on both sides of paper.
The printing data processor installed in the printer converts printing data in PDL form into printable data, such as bit images, to be printed on paper.
Printing data in a bit image, converted from printing data in PDL form, is supplied by the printing data processor. Here, the amount of memory used to store the supplied printing data greatly differs with the states of printing. For example, in color printing, memory four times greater than in monochrome printing is used. Therefore, processing time to obtain printing data in bit image form differs considerably.
The printing data processor performs a two-stage operation of an editing process and an expansion process on printing data in PDL form, to expand printing data to a printable bit image form. More specifically, printing data in PDL form is edited by the editing process and becomes printing data in intermediate form called a display list, for example. After this, printing data in this intermediate form is expanded by the expansion process to become printing data in bit image form for printing.
Meanwhile, in the prior art, there has been problems that require solution as described in the following.
The conventional printing data processor, before expanding printing data in PDL form to printable printing data, was unable to make a selection of, for example, whether to reproduce data on paper by color printing or by monochrome printing.
Therefore, before the expansion process it has been necessary to secure a maximum possible amount of memory to use. Another problem is that when color printing is selected, it requires longer processing time than monochrome printing, which results in decreases in the printing efficiency of the printer.